Negative resistance pulse repeater enclosed within a coaxial cable



March 30, 1965 R. A. HYMAN 3,176,076

NEGATIVE RESISTANCE PULSE REPEATER ENCLOSED WITHIN A COAXIAL CABLE Filed Aug. 22, 1962 2 Sheets-Sheet l 1 ig w r BC m 0 I 50 IW I50 C I 00% lfl aw g L6; //0' 15A Inventor ROBERT A. l/YMAN March 30, 1965 a A. HYMAN 3,176,076 NEGATIVE RESISTANCE PULSE REPEATER ENCLOSED WITHIN A COAXIAL CABLE 2 Sheets-Sheet 2 Filed Aug. 22, 1962 Inventor ROBERT A. HYMAN Aflorn y United States Patent NEGATIVE RESISTANCE PUISE REPEATER EN- CLOSED WITHIN A CQAXEAL (IABLE Robert Anthony Hyman, London, England, assignor to International Standard Electric Corporation, New York,

N.Y., a corporation of Deiaware Filed Aug. 22, 1962, Ser. No. 218,741 tilaims. (Eli. 179-15) This invention relates to intelligence transmission apparatus.

According to the invention intelligence transmission apparatus includes a series of electrical pulse regenerating units, each unit having means for storing electrical energy, means for releasing the electrical energy so stored upon the receipt of an electrical pulse input whereby the electrical energy so released provides an electrical pulse output, said output being applied to an adjacent pulse regenerating unit.

in one form of the invention the intelligence transmission apparatus provides an electrical pulse transmission line which includes -a series of pulse regenerating units, each unit comprising a capacitor capable of being charged from a bias voltage source, a negative resistance element arranged to discharge said capacitor when triggered by an electric pulse input, the resulting discharge from the capacitor being in efiect a re eneration of the input pulse and forrnin thereby a trigger pulse for an adjacent pulse regenerating unit.

In one form of construction of a pulse transmission line according to the invention there is provided a central core conductor, an intermediate cylindrical conductor and an outer cylindrical conductor, said conductor-s being coaxial, the space between the central and the intermediate conductors being filled with an active negative resistance material, the space between the intermediate and the outer conductors being filled with a resistive material the intermediate conductor being divided at equal intervals along its length mm a series of annular conductors, the individual sections of which are separated by insulating inserts.

in order that the invention may be more clearly understood a preferred embodiment thereof will now be de scribed with reference to the accompanying drawings in which:

FIG. 1 illustrates the voltage/ current characteristics of a negative resistance material as utilised in the invention, and

FIG. 2 is a circuit diagram of a simple form of the in vention, and

FIG. 3 is a longitudinal section of the construction of the preferred form of the invention, and

FIG. 4 is a cross-section of the construction shown in FIG. 3.

The term negative resistance as used in this specification refers to that class of materials or electronic device-s in which the voltage/current characteristics are similar to that depicted in FIG. 1. The voltage/current characteristic of most common electrical materials is determined by the application of Ghms law and is usually a straight line graph passing through zero and having a constant slope indicating that the current through the material increases with the applied voltage. There are, however, certain materials in which the voltage/current characteristics is not a continuous positive slope, but indicates that under certain conditions there is an increase in current through the material for a decrease in applied voltage. This porticn of the characteristic curve has a slope which is commonly described as negative and the material is therefore known as a negative resistance material. There are two types of negative resistance mate rial which are identified as voltage-controlled and current- 3,17%,02'6 Patented Mar. 30, 1965 controlled respectively, and it is the latter type of negative resistance which is utilised in the present invention. It the voltage/current characteristics of such a material is produced in graphical form it will appear to be similar to that shown in FIG. 1. That is to say for a given voltage the working point of the material on the curve is determinedtby the current through the material. Thus for a voltage V the working point will only be at P if the current through the material is I mil-liamps. If the current drawn through the material is I milliamps and the same voltage V is required, then the working point will be at Q on the curve. Similarly a current of I milliamps will determine a working point at S. However, the working point under a bias voltage of V will normally only be at Q unless a voltage pulse equal to the V volts is applied when the working point will move over the knee of the curve and will settle at either P or 3 depending on the current drawn.

If such a negative resistance is shunted across a charged capacitor, the charging voltage of which .is the same as the bias voltage of the negative resistance, for example V then the application of an electric pulse sufi'icient to cause the applied voltage to exceed temporarily V volts, the working point would move from C to a point some where in the region of S, which would change the material from being a high resistance material to a low resistance material. This effectively short circuits the charged capacitor causing a heavy but brief discharge, which in effeet is a regeneration of the trigger pulse. When the capacitor is discharged and the trigger pulse has been removed the voltage across the negative resistance will collapse and the material will re-assume its original high resistance condition by returning to point C under the influence of the bias voltage V which will at the same time re-chargc the capacitor.

In the circuit shown in FIG. 2 the capacitors 10a, lob, ltlc and Mid are charged through inductances 11a, ilb, Me and illd by a bias voltage V applied between the conductors 13 and 14. If a pulse suflicient to increase V momentarily to V, is applied to the coupling 15a the negative resistance 16:: will switch on and discharge the charged capacitor 10a. The resulting discharge will :form an effective pulse to switch diode 161) when applied thereto through a suitable coupling such as the capacitor 17a and attenuator 13a. In this manner the initial pulse received at the coupling 15a is regenerated and transmitted to the coupling 15b and so on down the transmission line.

It will be apparent that if the rate of ire-charging of the capacitor Illa is suificiently rapid, then the discharge or regenerated pulse provided by capacitor 1% is capable of switching on not only diode but also diode 16a, thus causing reflections in the line. This is overcome by having the circuit constants chosen such that. the capacitor in question cannot be sufiiciently recharged until the pulse has been transmitted for at least two or three succeeding stages along the line. Thus it will be seen that such a transmission line will be at any given moment unidirectional but it can be used alternatively from each end thus enabling it to be used as a bidirectional line for example for multiplex working.

Another 'feature of the invention is that a line constructed according to the circuit in FIG. 2 may be quite simply branched so that two or more outputs are available without the need for any extra equipment.

In addition the line may be made to operate as a delay line and pulse shaper or as a form of data store.

FIGS. 3 and 4 show the construction of a pulse transmission line corresponding to the circuit of FIG. 2. FIG. 3 is a longitudinal section on the centre line AA of FIG. 4 and FIG. 4 is a cross-section on the line B-B of FIG. 3. A central core conductor 2-8 is surrounded by a layer of active negative resistance material 21. The outer conduc- 1 ductor 24 at the termination of the line, the output being derived from the corresponding conductor 24 at the other end of the line. I

Each portion of the line comprising one section of the conductor 24 and the adjacent regions of active material 21 and resistive material23 comprise the equivalent of one pulse regenerating unit in FIG. 2, the insulating rings 25 providing the capacitativ'e coupling between the adjacent pulse regenerating units.

It will be appreciated that the invention is not limited to this particular form of construction, for example the line could be quite simply manufactured with the active material outermost and the resistive material surrounding the core.

A suitable negative resistance material for such a line may be, for example, compensated p-type germanium held at a temperature of 42 K. Such a line may conveniently have a layer of active material of radius 1 mm. operated with a bias voltage of 10 volts. In this example the resistive material may conveniently be graphite. Another form of construction of the line may use a gaseous active material such as a mixture of neon, argon and hydrogen, which exhibits suitable negative resistance properties when mixed in the approximate proportions 92: l :7. There 7 are many materials which have negative resistance propnular rings disposed intermediate said inner and outer conductors, a plurality of coaxial insulating discs disposed between said annular rings, an active negative resistance material filling the space between said inner conductor and said annular rings, a resistive material filling the space between said annular rings and said outer conductor, a source of direct current coupled between said inner and outer conductors, a source of pulses coupled to one end of said plurality of annular rings, each adjacent pair of said annular conductive rings forming a capacitor which is charged by said direct current and upon application of a pulse to said first annular conductive ring said capacitor is discharged, the resulting discharge forming in eifect a regeneration of the input pulse and forming thereby a trigger pulse for the next adjacent capacitor unit.

2. A pulse transmission line according to claim 1 but having the active negative resistance material between said annular rings and the outer conductors and the resistive material between said annular rings and said inner conductors.

3. A pulse transmission line according to claim 2 in which the active negative resistance material is compensated p-type germanium held at a temperature of 42 K.

4. A pulse transmission line according to claim 2 in which the active negative resistance material is a gaseous mixture of neon, argon and hydrogen.

5. A pulse transmission line according to claim 2 in which the resistive material is graphite.

7/63 Nelson 307-4585 DAVID G. REDINBAUGH, Primary Examiner. V 

1. A PULSE TRANSMISSION LINE COMPRISING INNER AND OUTER COAXIAL CONDUCTORS, A PLURALITY OF COAXIAL CONDUCTIVE ANNULAR RINGS DISPOSED INTERMEDIATE SAID INNER AND OUTER CONDUCTORS, A PLURALITY OF COAXIAL INSULATING DISCS DISPOSED BETWEEN SAID ANNULAR RINGS, AN ACTIVE NEGATIVE RESISTANCE MATERIAL FILLING THE SPACE BETWEEN SAID INNER CONDUCTOR AND SAID ANNULAR RINGS, A RESISTIVE MATERIAL FILLING THE SPACE BETWEEN SAID ANNULAR RINGS AND SAID OUTER CONDUCTOR, A SOURCE OF DIRECT CURRENT COUPLED BETWEEN SAID INNER AND OUTER CONDUCTORS, A SOURCE OF PULSES COUPLED TO ONE END OF SAID PLURALITY OF ANNULAR RINGS, EACH ADJACENT PAIR OF SAID ANNULAR CONDUCTIVE RINGS FORMING A CAPACITOR WHICH IS CHARGED BY SAID DIRECT CURRENT AND UPON APPLICATION OF A PULSE TO SAID FIRST ANNULAR CONDUCTIVE RING SAID CAPACITOR IS DISCHARGED, THE RESULTING DISCHARGE FORMING IN EFFECT A REGENERATION OF THE INPUT PULSE AND FORMING THEREBY A TRIGGER PULSE FOR THE NEXT ADJACENT CAPACITOR UNIT. 